Our Solar System

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IntroductionA solar system is a star and all of the objects that travel around it—planets, moons, asteroids, comets and meteoroids. Most stars host their own planets, so there are likely tens of billions of other solar systems in the Milky Way galaxy alone. Solar systems can also have more than one star. These are called binary star systems if there are two stars, or multi-star systems if there are three or more stars.

The solar system we call home is located in an outer spiral arm of the vast Milky Way galaxy. It consists of the Sun (our star) and everything that orbits around it. This includes the eight planets and their natural satellites (such as our moon), dwarf planets and their satellites, as well as asteroids, comets and countless particles of smaller debris. Explore Our Solar System ›

Ten Things to Know

Ten Things to Know About Our Solar System

1

One of Billions

Our solar system is made up of a star, eight planets and countless smaller bodies such as dwarf planets, asteroids and comets.

2

Meet Me in the Orion Arm

Our solar system orbits the center of the Milky Way Galaxy at about 515,000 mph (828,000 kph). We’re in one of the galaxy’s four spiral arms.

3

A Long Way Round

It takes our solar system about 230 million years to complete one orbit around the galactic center.

4

Spiraling Through Space

There are three general kinds of galaxies: elliptical, spiral and irregular. The Milky Way is a spiral galaxy.

5

Good Atmosphere(s)

Our solar system is a region of space. It has no atmosphere. But it contains many worlds—including Earth—with many kinds of atmospheres.

6

Many Moons

The planets of our solar system—and even some asteroids—hold more than 150 moons in their orbits.

7

Ring Worlds

The four giant planets—and at least one asteroid—have rings. None are as spectacular as Saturn’s gorgeous rings.

8

Leaving the Cradle

More than 300 robotic spacecraft have explored destinations beyond Earth orbit, including 24 astronauts who orbited the moon.

9

Life as We Know It

Our solar system is the only one known to support life. So far, we only know of life on Earth, but we’re looking for more everywhere we can.

10

Far-Ranging Robots

NASA’s Voyager 1 is the only spacecraft so far to leave our solar system. Four other spacecraft will eventually hit interstellar space.

Did You Know

Did You Know?

Five spacecraft have achieved enough velocity to travel beyond the boundaries of our solar system. Voyager 1 crossed into interstellar space in 2012. Voyager 2 and New Horizons are still active and will eventually transition to the space between the stars. Pioneers 10 and 11 also have reached escape velocity, but both spacecraft have been inactive for many years